Dynamic testing device for three-dimensional stress state of unsaturated soil and its implementation method

Abstract

The present invention provides a dynamic test device for the three-dimensional stress state of unsaturated soil and an implementation method thereof. The device is based on the relationship between principal stress and stress state, combined with the isotropic basis of matrix suction and pore water pressure, and weakens the influence of stress concentration on the test results through a spherical structure. The dual-mode equivalent method is used to realize the conversion between curved surface and plane force, and the inclination sensing technology is used to quantify the error caused by the rotation of the device. At the same time, an implementation method of the dynamic test device for the three-dimensional stress state of unsaturated soil is provided. The beneficial effects of the present invention are: reducing the influence of stress concentration on the device skeleton and test results and the error caused by the position change of soil particles embedded in the stressed diaphragm; the vector calculation method reduces the complexity of calculation; the method of selecting the test direction in multiple directions improves the accuracy of the principal stress test, thereby improving the accuracy of measuring the internal stress state of the soil under the unsaturated state, and providing guarantee for the safe construction and reliable operation of geotechnical engineering.

Description

Technical Field

[0001] The present invention belongs to the field of three-dimensional soil pressure testing, and specifically relates to a three-dimensional stress state dynamic testing device for unsaturated soil and an implementation method thereof, which is applicable to the fields of rock and soil mechanics and engineering. Technical Background

[0002] Unsaturated soil is a multiphase body composed of soil particles, water and gas, saturated soil is a two-phase body composed of soil particles and water, and dry soil is a two-phase body composed of soil particles and gas. In general, the land surface involves unsaturated soil or nearly saturated soil problems. Unsaturated soil is the most widely existing soil, and saturated soil and dry soil are only a special state of unsaturated soil. The measurement of stress state is the basis for determining the direction and magnitude of the maximum principal stress, and is the basis for evaluating the stability of soil structure. Therefore, providing a three-dimensional stress state that can be measured inside the soil under an unsaturated state plays an important role in improving the safety of engineering construction and ensuring the reliability of engineering monitoring and detection.

[0003] The current three-dimensional soil pressure test device has the following shortcomings: ① It is attached to an angular base, such as the Chinese patents with publication numbers CN106442104A, CN105606261A, and CN109443604A, which cannot eliminate the stress concentration problem of the base; ② It can measure the total stress or the effective stress state of saturated soil, such as the Chinese patents with publication numbers CN106248267A, CN105403330A, CN109990941A, and C N109443604A, but cannot determine the effective stress state of unsaturated soil; ③ cannot exclude the error caused by the angle change of the test device during the test, such as the Chinese patents with publication numbers CN108169458A and CN109990941A; or there are problems of complex calculations, such as the Chinese patent with publication number CN106525297A; or there are problems of calculation errors, such as the Chinese patent with publication number CN109443604, when θ, When δ is 0, the result obtained by formula (6) is not the unit matrix, that is, formula (1) still needs to be corrected, that is, the test result is also rotated when no rotation occurs; ④ The influence of the change in the number of contact interfaces between particles and pressure sensors on the results during the force process cannot be considered, such as the Chinese patents with publication numbers CN109990941A and CN109443604A; ⑤ The reflection of the anisotropy of the soil on the true stress state of a point cannot be considered, such as the Chinese patents with publication numbers CN109990941A and CN109443604A. This type of problem causes an error between the test result and the true value, making the understanding of the three-dimensional stress state of a point in unsaturated soil inaccurate.

[0004] To overcome the above shortcomings, the following issues must be addressed: ① The surface of the sensor should be smoother to reduce stress concentration; ② The pore water pressure and matrix suction of the soil should be measured; ③ The angle change of the sensor during the test should be determined; ④ The trace errors caused by soil particles embedded in the test diaphragm should be eliminated; ⑤ The stress value in the main force direction or coordinate direction should be directly measured. Summary of the invention

[0005] In view of the above-mentioned shortcomings, an object of the present invention is to provide a dynamic testing device for the three-dimensional stress state of unsaturated soil and an implementation method thereof, so as to improve the measurement accuracy of the three-dimensional stress state inside the unsaturated soil.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a dynamic test device for the three-dimensional stress state of unsaturated soil, the device comprising: a spherical body, an arc elastic diaphragm, a lower plane elastic diaphragm, hydraulic oil, an arc water-permeable plate, an arc clay plate, a high-sensitivity elastic diaphragm, an annular strain gauge, an arc-shaped inclination sensor, and a data conductor; the spherical body has a spherical appearance, and 26 cylindrical grooves of the same size are opened on the surface, wherein there is one cylindrical groove on the top surface and one cylindrical groove on the bottom surface, and the other 24 cylindrical grooves are evenly divided into three layers of upper, middle and lower layers, which are symmetrical about the cylindrical grooves on the top surface and the cylindrical grooves on the bottom surface. The cylindrical groove is distributed on the spherical body; a transparent circular hole smaller than the diameter of the circular groove is opened at the bottom of the cylindrical groove, and a sensor data wire channel is opened in the circular hole toward the center of the spherical body; the annular strain gauge is pasted on the outside of the high-sensitivity elastic diaphragm, and the signal line of the annular strain gauge is connected with the data wire, and the high-sensitivity elastic diaphragm pasted with the annular strain gauge is arranged at the bottom of two adjacent cylindrical grooves in the middle layer of the spherical body and connected to the circular hole, and the arc water-permeable plate and the arc clay plate are arranged on the upper part of the high-sensitivity elastic diaphragm respectively, and the arc water-permeable plate and the spherical body and the gap between the arc clay plate and the spherical body are respectively connected. The gap is filled with sealant to ensure that the water vapor pressure is transmitted to the high-sensitivity elastic diaphragm through the circular arc water-permeable plate and the circular arc clay plate, respectively, wherein the outer surfaces of the circular arc water-permeable plate and the circular arc clay plate are flush with the surface of the spherical body; the circular arc tilt angle sensor is arranged in the cylindrical groove adjacent to the cylindrical groove of the circular arc clay plate in the middle layer, and the outer surface of the circular arc tilt angle sensor is flush with the surface of the spherical body; the annular strain gauge is pasted on the outer side of the lower plane elastic diaphragm, the edge of the circular arc elastic diaphragm is connected to the edge of the lower plane elastic diaphragm, and the hydraulic oil is filled between the circular arc elastic diaphragm and the lower plane elastic diaphragm. The cavity between the two spherical bodies is formed by connecting the signal line of the annular strain gauge with the data wire, thereby forming a double-membrane sensor; the double-membrane sensor is arranged in the remaining 22 cylindrical grooves except the bottom cylindrical groove, and the outer surface of the arc elastic diaphragm of the double-membrane sensor is flush with the surface of the spherical body; the data wire of the arc-shaped inclination sensor and the data wire of the annular strain gauge are passed through the cylindrical groove at the bottom of the spherical body to be connected with the external acquisition system, and the pore between the data wire and the cylindrical groove at the bottom of the spherical body is filled with sealant, thereby forming the unsaturated soil three-dimensional stress state dynamic test device.

[0007] A support ring is provided on the inner edge of the circular arc water-permeable plate so that the circular arc water-permeable plate does not directly contact the high-sensitivity elastic diaphragm; a clay plate support ring is provided on the inner edge of the circular arc clay plate so that the circular arc clay plate does not directly contact the high-sensitivity elastic diaphragm; the lower plane elastic diaphragm and the high-sensitivity elastic diaphragm are both divided into an outer fixing ring and a circular test area, and the annular strain gauge is pasted within 0.577 times the radius of the circular test area of ​​the lower plane elastic diaphragm and the high-sensitivity elastic diaphragm according to central symmetry.

[0008] An implementation method of a three-dimensional stress state dynamic testing device for unsaturated soil, the method comprising the following steps:

[0009] 1) Arrange the unsaturated soil three-dimensional stress state dynamic test device and connect the data wire to the acquisition system;

[0010] 2) Take the center of the spherical body as the origin, the line connecting the middle points of the top and bottom surfaces of the spherical body as the positive direction of the z-axis, and the line connecting the origin and the center of the arc-shaped inclination sensor surface as the positive direction of the x-axis. Establish a spatial rectangular coordinate system according to the right-hand system, and number the cylindrical grooves on the spherical body, where A u A is a cylindrical groove with an arc-shaped water-permeable plate. s A is a cylindrical groove with arc clay plates. T The cylindrical grooves are provided with arc-shaped inclination sensors. A1 is the cylindrical groove at the top of the spherical body. A2, A3, A4, A5, and A6 are the five adjacent cylindrical grooves in the middle layer of the spherical body starting from the cylindrical groove adjacent to the cylindrical groove of the arc-shaped water-permeable plate in the clockwise direction. A7, A8, A9, and A 10 , A 11 , A 12 , A 13 , A 14 A is arranged on the upper layer of the spherical body, starting from the cylindrical groove adjacent to the cylindrical groove of the arc water-permeable plate in the clockwise direction, and 15 , A 16 , A 17 , A 18 , A 19 , A 20 , A 21 , A 22 8 adjacent cylindrical grooves arranged in the lower layer of the spherical body in a clockwise direction starting from the cylindrical groove adjacent to the cylindrical groove of the arc water-permeable plate;

[0011] 3) Turn on the acquisition system and balance the degree of the arc-shaped inclination sensor according to the spatial rectangular coordinate system established in step 2), and then bury the balanced unsaturated soil three-dimensional stress state dynamic test device into the unsaturated soil body;

[0012] 4) The double-film sensor arranged on the cylindrical groove can measure the double-film sensor test value σ in 22 directions i, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, where σ1 is the test value of the double-film sensor arranged on the cylindrical groove of the spherical body A1, σ2, σ3, σ4, σ5, σ6 are the test values ​​of the double-film sensors arranged on the cylindrical grooves of the spherical bodies A2, A3, A4, A5, A6, σ7, σ8, σ9, σ10 are the test values ​​of the double-film sensors arranged on the cylindrical grooves of the spherical bodies A2, A3, A4, A5, A6, σ11, σ12, σ13, σ14, σ15, σ16 are the test values ​​of the double-film sensors arranged on the cylindrical grooves of the spherical bodies A2, A3, A4, A5, A6, σ17, σ18, σ19, σ20, σ21, σ22 10 , σ 11 , σ 12 , σ 13 , σ 14 For arrangement on the spherical bodies A7, A8, A9, A 10 , A 11 , A 12 , A 13 , A 14 Test value of double-film sensor on cylindrical groove, σ 15 , σ 16 , σ 17 , σ 18 , σ 19 , σ 20 , σ 21 , σ 22 Arranged in the spherical body A 15 , A 16 , A 17 , A 18 , A 19 , A 20 , A 21 , A 22 Test value of double-film sensor on cylindrical groove, σ u Arranged in the spherical body A u Test value of strain gauge sensor on cylindrical groove, σ s Arranged in the spherical body A s The test values ​​of the strain gauge sensor on the cylindrical groove, θ, η, ζ are arranged on the spherical body A T The angles around the z, y, and x axes collected by the arc-shaped inclination sensor on the cylindrical groove;

[0013] 5) Using formula (1), calculate σ on the dynamic test device for three-dimensional stress state of unsaturated soil i The effective stress value σ in the direction i ', where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, formula (1) is:

[0014] σ′ i =σ i -(σ s +σu )+S e σ s (1)

[0015] In the formula, σ i ' is the A value of the dynamic test device for the three-dimensional stress state of unsaturated soil i Effective stress values ​​on cylindrical grooves, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, σ i Arranged in the spherical body A i Test value of double-film sensor on cylindrical groove, σ u Arranged in the spherical body A u Test value of strain gauge sensor on cylindrical groove, σ s Arranged in the spherical body A s Test value of strain gauge sensor on cylindrical groove, S e is the effective degree of saturation of unsaturated soil;

[0016] 6) Based on the spatial rectangular coordinate system established in step 2), σ i Direction is the unit vector through the origin Expressed as follows, where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22;

[0017] 7) Use formula (2) to convert the dynamic test direction vector of the dynamic test device for three-dimensional stress state of unsaturated soil into Expressed as follows, formula (2) is:

[0018]

[0019] In the formula, is the dynamic test direction vector of the dynamic test device for three-dimensional stress state of unsaturated soil, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, θ, η, ζ are arranged on the spherical body A respectively T The arc-shaped inclination sensor of the cylindrical groove collects the angles around the z, y, and x axes. The unit vector whose direction passes through the origin;

[0020] 8) The direction cosine D of the dynamic test direction of the dynamic test device for three-dimensional stress state of unsaturated soil i {l i ',m i ',n i'} Calculated using formulas (3), (4), and (5), the formula is:

[0021]

[0022]

[0023]

[0024] In the formula, l i '、m i '、n i ' is the direction cosine of the dynamic test direction of the dynamic test device for three-dimensional stress state of unsaturated soil, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, is the dynamic test direction vector of the dynamic test device for the three-dimensional stress state of unsaturated soil, is the modulus of the dynamic test direction vector of the dynamic test device for the three-dimensional stress state of unsaturated soil, are the unit vectors on the x, y, and z axes respectively, are the magnitudes of the unit vectors on the x, y, and z axes respectively;

[0025] 9) Select 6 different direction cosines D i {l i ',m i ',n i '} Construct the transformation matrix M shown in formula (6), where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, and denote the selected direction cosines as D i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',mi6 ',n i6 '}, formula (6) is:

[0026]

[0027] Where M is the transformation matrix, D i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '} are 6 different direction cosines selected, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22;

[0028] 10) Calculate the inverse matrix M of the matrix M in formula (6) 1 , and the dynamic value {σ} of the three-dimensional stress state of unsaturated soil is calculated according to formula (7), which is:

[0029] {σ}=M- 1 ·{σ′ ij} (7)

[0030] Where {σ} is the dynamic value of the three-dimensional stress state of unsaturated soil, M- 1 is the inverse matrix of matrix M, {σ′ ij} is the direction cosine D in step 9) determined according to formula (1) i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',mi3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '} The effective stress value σ in the direction corresponding to i ', i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, j is 6 different direction cosines D i {l i ',m i ',n i '} are numbered in sequence, j=1, 2, 3, 4, 5, 6.

[0031] The effects of the present invention are that the three-dimensional stress state dynamic test device for unsaturated soil adopts a spherical appearance, which reduces the influence of stress concentration on the device skeleton and test results; adopts a buffer dual-mode mode of incompressible hydraulic oil to reduce the test error caused by soil particles embedded in the stress-bearing diaphragm; adopts a vector calculation method to reduce the complexity of calculation; adopts a multi-directional selection of test directions to improve the accuracy of principal stress testing; and realizes the dynamic test of the three-dimensional stress state of unsaturated soil. If the test accuracy of a single annular strain gauge is k, the test accuracy of the three principal stresses is k in the eight horizontal directions, and the worst angle of the calculated true value is 22.5°, and the range is better than the minimum internal friction angle range of the soil. The improvement in accuracy can maximize the accuracy of stress state measurement inside the soil under unsaturated state, providing guarantee for the safe construction and reliable operation of geotechnical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a cross-sectional view of the dynamic testing device for three-dimensional stress state of unsaturated soil of the present invention;

[0033] Figure 2 It is a top view schematic diagram of the unsaturated soil three-dimensional stress state dynamic testing device of the present invention;

[0034] Figure 3 It is a bottom view schematic diagram of the unsaturated soil three-dimensional stress state dynamic testing device of the present invention;

[0035] Figure 4 is a cross-sectional schematic diagram of a double-membrane sensor of the present invention;

[0036] Figure 5 It is a cross-sectional schematic diagram of the arc water-permeable plate / clay plate of the present invention;

[0037] Figure 6 It is a schematic diagram of the inner side plane of the high-sensitivity / flat elastic diaphragm of the present invention.

[0038] In the figure:

[0039] 1. Spherical body 2. Arc elastic diaphragm 3. Planar elastic diaphragm

[0040] 4. Hydraulic oil 5. Arc permeable board 6. Arc clay board

[0041] 7. Highly sensitive elastic diaphragm 8. Annular strain gauge 9. Arc-shaped inclination sensor

[0042] 10. Data wire 11. Circular groove 12. Sensor data wire channel

[0043] 21.Dual membrane sensor 31.Outer fixing ring 32.Circular test area

[0044] 111. Round hole 112. Sealant DETAILED DESCRIPTION

[0045] The unsaturated soil three-dimensional stress state dynamic testing device and its implementation method of the present invention are described in conjunction with the accompanying drawings.

[0046] The design principle of the dynamic testing device for the three-dimensional stress state of unsaturated soil and its implementation method of the present invention is: based on the relationship between principal stress and stress state, combined with the isotropic basis of matrix suction and pore water pressure, it is proposed to weaken the influence of stress concentration on the test results through the appearance of a sphere, and the dual-mode equivalent method is used to realize the conversion between curved surface and plane force, and then calculate and obtain the three-dimensional stress state of unsaturated soil.

[0047] The specific implementation methods of the unsaturated soil three-dimensional stress state dynamic testing device and its implementation method of the present invention are as follows:

[0048] like Figure 1-3The unsaturated soil three-dimensional stress state dynamic testing device shown in the figure comprises: a spherical body 1, an arc elastic diaphragm 2, a lower plane elastic diaphragm 3, hydraulic oil 4, an arc water-permeable plate 5, an arc clay plate 6, a high-sensitivity elastic diaphragm 7, an annular strain gauge 8, an arc-shaped inclination sensor 9, and a data conductor 10; the spherical body 1 has a spherical appearance, and has 26 cylindrical grooves 11 of the same size on the surface, wherein there is one cylindrical groove 11 on the top surface and one cylindrical groove 11 on the bottom surface, and the other 24 cylindrical grooves 11 are evenly divided into three parts: upper, middle, and lower. The layers are symmetrically distributed on the spherical body 1 about the top cylindrical groove 11 and the bottom cylindrical groove 11; a transparent circular hole 111 smaller than the diameter of the circular groove is opened at the bottom of the cylindrical groove 11, and a sensor data wire channel 12 is opened in the circular hole 111 toward the center of the spherical body 1; the annular strain gauge 8 is pasted on the outside of the high-sensitivity elastic diaphragm 7, and the signal line of the annular strain gauge 8 is connected to the data wire 10, and the high-sensitivity elastic diaphragm 7 pasted with the annular strain gauge 8 is arranged on two adjacent circular diaphragms in the middle layer of the spherical body 1. The bottom of the cylindrical groove 11 is connected to the circular hole 111, and the arc water-permeable plate 5 and the arc clay plate 6 are arranged on the upper part of the high-sensitivity elastic diaphragm 7 respectively, and the gaps between the arc water-permeable plate 5 and the spherical body 1 and the arc clay plate 6 and the spherical body 1 are filled with sealant 112 to ensure that the water vapor pressure is transmitted to the high-sensitivity elastic diaphragm 7 through the arc water-permeable plate 5 and the arc clay plate 6 respectively, wherein the outer surfaces of the arc water-permeable plate 5 and the arc clay plate 6 are flush with the surface of the spherical body 1; the arc-shaped inclination sensor 9 is arranged The circular arc tilt sensor 9 is placed in the cylindrical groove 11 adjacent to the cylindrical groove 11 of the arc clay plate 6 in the middle layer, and the outer surface of the arc tilt sensor 9 is flush with the surface of the spherical body 1; the annular strain gauge 8 is pasted on the outer side of the lower plane elastic diaphragm 3, the edge of the arc elastic diaphragm 2 is connected to the edge of the lower plane elastic diaphragm 3, and the hydraulic oil 4 is filled in the cavity between the arc elastic diaphragm 2 and the lower plane elastic diaphragm 3, and the signal line of the annular strain gauge 8 is connected to the data wire 10, so as to form a double membrane sensor 21, as shown in FIG. Figure 4 As shown; the double-membrane sensor 21 is arranged in the remaining 22 cylindrical grooves 11 except the bottom cylindrical groove 11, and the outer surface of the arc elastic diaphragm 2 of the double-membrane sensor 21 is flush with the surface of the spherical body 1; the data wire 10 of the arc-shaped inclination sensor 9 and the data wire 10 of the annular strain gauge 8 are passed through the cylindrical groove 11 at the bottom of the spherical body 1 to connect with the external acquisition system, and the pores between the data wire 10 and the cylindrical groove 11 at the bottom of the spherical body 1 are filled with sealant 112, thereby forming the unsaturated soil three-dimensional stress state dynamic test device.

[0049] The inner edge of the arc water-permeable plate 5 is provided with a support ring 51 so that the arc water-permeable plate 5 does not directly contact the high-sensitivity elastic diaphragm 7. Figure 5As shown; the inner edge of the arc clay plate 6 is provided with a clay plate support ring 61, so that the arc clay plate 6 is not directly in contact with the high-sensitivity elastic diaphragm 7; the lower plane elastic diaphragm 3 and the high-sensitivity elastic diaphragm 7 are divided into an outer fixing ring 31 and a circular test area 32, as shown Figure 6 As shown; the annular strain gauge 8 is pasted on the lower plane elastic diaphragm and the high-sensitivity elastic diaphragm 7 within 0.577 times the radius of the circular test area 32 according to the central symmetry.

[0050] The implementation method of the dynamic testing device for three-dimensional stress state of unsaturated soil comprises the following steps:

[0051] 1) Assembling the unsaturated soil three-dimensional stress state dynamic test device and connecting the data conductor 10 to the acquisition system;

[0052] 2) With the center of the spherical body 1 as the origin, the line connecting the middle points of the top and bottom surfaces of the spherical body 1 as the positive direction of the z-axis, and the line connecting the origin and the center of the surface of the arc-shaped inclination sensor 9 as the positive direction of the x-axis, a spatial rectangular coordinate system is established according to the right-hand system, and the cylindrical grooves 11 on the spherical body 1 are numbered, where A u A is a cylindrical groove 11 with an arc water-permeable plate 5. s A is a cylindrical groove 11 in which a circular arc clay plate 6 is arranged. T The cylindrical grooves 11 are provided with arc-shaped inclination sensors 9, A1 is the cylindrical groove 11 at the top of the spherical body 1; A2, A3, A4, A5, A6 are five adjacent cylindrical grooves 11 in the middle layer of the spherical body 1 starting from the cylindrical groove 11 adjacent to the cylindrical groove 11 of the arc-shaped water-permeable plate 5 in the clockwise direction, A7, A8, A9, A 10 , A 11 , A 12 , A 13 , A 14 The eight adjacent cylindrical grooves 11 arranged on the upper layer of the spherical body 1 and starting from the cylindrical groove 11 adjacent to the cylindrical groove 11 of the arc water-permeable plate 5 in the clockwise direction, A 15 , A 16 , A 17 , A 18 , A 19 , A 20 , A 21 , A 22 The eight adjacent cylindrical grooves 11 are arranged in the lower layer of the spherical body 1 and are arranged in a clockwise direction starting from the cylindrical groove 11 adjacent to the cylindrical groove 11 of the arc water-permeable plate 5;

[0053] 3) Turn on the acquisition system and balance the degree of the arc-shaped inclination sensor 9 according to the spatial rectangular coordinate system established in step 2), and then bury the balanced unsaturated soil three-dimensional stress state dynamic test device into the unsaturated soil body;

[0054] 4) Determine the test value σ of the double-film sensor 21 in 22 directions according to the double-film sensor 21 arranged on the cylindrical groove 11 i , i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, wherein σ1 is the test value of the double-film sensor 21 arranged on the cylindrical groove 11 of the spherical body 1A1, σ2, σ3, σ4, σ5, σ6 are the test values ​​of the double-film sensor 21 arranged on the cylindrical groove 11 of the spherical body 1A2, A3, A4, A5, A6, σ7, σ8, σ9, σ10 are the test values ​​of the double-film sensor 21 arranged on the cylindrical groove 11 of the spherical body 1A2, A3, A4, A5, A6, σ11, σ12, σ13, σ14, σ15, σ16 are the test values ​​of the double-film sensor 21 arranged on the cylindrical groove 11 of the spherical body 1A2, A3, A4, A5, A6, σ17, σ18, σ19, σ20, σ21 10 , σ 11 , σ 12 , σ 13 , σ 14 For arrangement on the spherical bodies 1A7, A8, A9, A 10 , A 11 , A 12 , A 13 , A 14 Test value of the double-film sensor 21 on the cylindrical groove 11, σ 15 , σ 16 , σ 17 , σ 18 , σ 19 , σ 20 , σ 21 , σ 22 To be arranged on the spherical body 1A 15 , A 16 , A 17 , A 18 , A 19 , A 20 , A 21 , A 22 Test value of the double-film sensor 21 on the cylindrical groove 11, σ u To be arranged on the spherical body 1A u Test value of strain gauge sensor on cylindrical groove 11, σ s To be arranged on the spherical body 1A s The test values ​​of the variable chip sensor on the cylindrical groove 11, θ, η, ζ are respectively arranged on the spherical 1A T The angles around the z, y, and x axes collected by the arc-shaped inclination sensor 9 on the cylindrical groove 11;

[0055] 5) Using formula (1), calculate σ on the dynamic test device for three-dimensional stress state of unsaturated soili The effective stress value σ in the direction i ', where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, formula (1) is:

[0056] σ′ i =σ i -(σ s +σ u )+S e σ s (1)

[0057] σ′ i =σ i -(σ s +σ u )+χσ s (2)

[0058] In the formula, σ i ' is the A value of the dynamic test device for the three-dimensional stress state of unsaturated soil i The effective stress values ​​on the cylindrical groove 11, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, σ i To be arranged on the spherical body 1A i Test value of the double-film sensor 21 on the cylindrical groove 11, σ u To be arranged on the spherical body 1A u Test value of the highly sensitive elastic diaphragm 7 on the cylindrical groove 11, σ s To be arranged on the spherical body 1A s Test value of the highly sensitive elastic diaphragm 7 on the cylindrical groove 11, S e is the effective saturation of unsaturated soil, χ is the soil saturation related parameter;

[0059] 6) Based on the spatial rectangular coordinate system established in step 2), σ i Direction is the unit vector through the origin Expressed as follows, where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22;

[0060] 7) Use formula (3) to convert the dynamic test direction vector of the dynamic test device for three-dimensional stress state of unsaturated soil into Expressed as follows, formula (3) is:

[0061]

[0062] In the formula, is the dynamic test direction vector of the dynamic test device for three-dimensional stress state of unsaturated soil, i=1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, θ, η, ζ are arranged on the spherical body 1A respectively T The angles around the z, y, and x axes collected by the arc-shaped inclination sensor 9 on the cylindrical groove 11 are is i A unit vector whose direction passes through the origin;

[0063] 8) The direction cosine D of the dynamic test direction of the dynamic test device for three-dimensional stress state of unsaturated soil i {l i ',m i ',n i '} Calculated using formulas (4), (5), and (6), the formula is:

[0064]

[0065]

[0066]

[0067] In the formula, l i '、m i '、n i ' is the direction cosine of the dynamic test direction of the dynamic test device for three-dimensional stress state of unsaturated soil, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, is the dynamic test direction vector of the dynamic test device for the three-dimensional stress state of unsaturated soil, is the modulus of the dynamic test direction vector of the dynamic test device for the three-dimensional stress state of unsaturated soil, are the unit vectors on the x, y, and z axes respectively, are the magnitudes of the unit vectors on the x, y, and z axes respectively;

[0068] 9) Select 6 different direction cosines D i {l i ',m i ',n i '} Construct the transformation matrix M shown in formula (7), where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, and denote the selected direction cosines as D i1 {l i1 ',m i1',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '}, formula (7) is:

[0069]

[0070] Where M is the transformation matrix, D i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '} are 6 different direction cosines selected, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22;

[0071] 10) Calculate the inverse matrix M of the matrix M in formula (7) -1 , and the dynamic value {σ} of the three-dimensional stress state of unsaturated soil is calculated according to formula (8), which is:

[0072] {σ}=M-1 ·{σ′ ij} (8)

[0073] Where {σ} is the dynamic value of the three-dimensional stress state of unsaturated soil, M -1 is the inverse matrix of matrix M, {σ′ ij} is the direction cosine D in step 9) determined according to formula (1) i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '} The effective stress value σ in the direction corresponding to i ', i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, j is 6 different direction cosines D i {l i ',m i ',n i '} are numbered in sequence, j=1, 2, 3, 4, 5, 6.

[0074] The technical features of the present invention are:

[0075] (1) The spherical appearance reduces the impact of stress concentration on the device frame and test results;

[0076] (2) The dual-mode buffering mode of incompressible hydraulic oil is adopted to reduce the error caused by soil particles embedded in the stressed diaphragm;

[0077] (3) The use of vector computing reduces the complexity of data calculation;

[0078] (4) Ability to correct the accuracy of calculation results by testing principal stresses in different orientations;

[0079] (5) Taking into account the test error caused by the rotation of the device during the burial and testing process, dynamic determination of the three-dimensional stress state in unsaturated soil is achieved.

[0080] If the test accuracy of a single annular strain gauge is k, then the test accuracy of the three principal stresses is k in the eight horizontal directions, and the worst angle of the estimated true value is 22.5°, which is better than the minimum internal friction angle range of the soil. The improvement in accuracy can maximize the accuracy of stress state measurement inside the soil under unsaturated conditions, providing guarantee for the safe construction and reliable operation of geotechnical engineering.

[0081] The above description is only for illustration in conjunction with this production process and does not limit this structure. For those skilled in the art, the present invention may have various changes and modifications, such as specifying the installation surface to certain directions, replacing the annular strain gauge with a vibrating wire, adding sensor calibration in the implementation method, etc. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dynamic testing device for three-dimensional stress state of unsaturated soil, comprising: A spherical body (1) and a data conductor (10), characterized in that: the outer surface of the spherical body (1) is provided with a plurality of cylindrical grooves (11); the bottom circular holes (111) of the cylindrical grooves (11) are all provided with through holes and form a sensor data conductor channel (12) with the center of the spherical body; the data conductor (10) is gathered at the center of the spherical body (1) and then led out through the bottom channel and the cylindrical groove (11); the cylindrical groove (11) is provided with an arc-shaped inclination sensor (9), a strain gauge sensor or a double-film sensor (21); the double-film sensor includes a sensor arranged in the cylindrical groove (11) an upper circular arc elastic diaphragm (2) and a lower flat elastic diaphragm (3), the edges of the upper circular arc elastic diaphragm (2) and the lower flat elastic diaphragm (3) are respectively sealed and connected to the inner wall of the cylindrical groove (11), a chamber for hydraulic oil (4) is formed between the circular arc elastic diaphragm (2) and the lower flat elastic diaphragm, and an annular strain gauge (8) is adhered to the outer side of the lower flat elastic diaphragm; the strain gauge sensor comprises an arc plate arranged on the upper layer of the cylindrical groove (11), the lower flat elastic diaphragm (3) and an annular strain gauge (8) outside the lower flat elastic diaphragm (3).

2. The unsaturated soil three-dimensional stress state dynamic testing device according to claim 1 is characterized by: The arc plate of the upper layer is an arc water-permeable plate (5) or an arc clay plate (6), and the outer surface is flush with the surface of the spherical body (1); the inner edge of the arc water-permeable plate (5) is provided with a support ring (51), and the inner edge of the arc clay plate (6) is provided with a clay plate support ring (61); the arc water-permeable plate (5) and the arc clay plate (6) are sealedly connected to the spherical body (1), and the lower layer planar elastic diaphragm (3) is a highly sensitive elastic diaphragm (7).

3. The unsaturated soil three-dimensional stress state dynamic testing device according to claim 1 is characterized by: The lower plane elastic diaphragm (3) and the high-sensitivity elastic diaphragm (7) are both divided into an outer fixing ring (31) and a circular test area (32); the annular strain gauge (8) is symmetrically attached to the center of the circular test area (32) of the lower plane elastic diaphragm (3) or the high-sensitivity elastic diaphragm (7) and has a length within 0.577 times the radius of the circular test area (32).

4. The three-dimensional stress state dynamic testing device of unsaturated soil according to claim 1 is characterized by: The plurality of cylindrical grooves (11) are provided in 26 numbers, one each at the top and bottom of the spherical body (1), and the remaining 24 cylindrical grooves (11) are divided into three layers, namely, upper, middle and lower, and are symmetrically distributed on the spherical body (1).

5. The unsaturated soil three-dimensional stress state dynamic testing device according to claim 4 is characterized by: Strain gauge sensors arranged with arc-shaped water-permeable plates (5) or arc-shaped clay plates (6) are arranged in two cylindrical grooves (11) in the middle layer of the three layers, an arc-shaped inclination sensor (9) is arranged in a cylindrical groove (11) adjacent to the strain gauge sensor arranged with the arc-shaped clay plate (6), the cylindrical groove (11) at the bottom of the spherical body (1) serves as a sensor data conductor (10) channel, and double-membrane sensors (21) are arranged in the remaining cylindrical grooves (11).

6. The unsaturated soil three-dimensional stress state dynamic testing device according to claim 5 is characterized by: The outer surface of the spherical body (1) is flush with the outer surface of the arc elastic diaphragm (2), the arc water-permeable plate (5), the arc clay plate (6) or the arc-shaped tilt sensor (9) on the upper layer of the cylindrical groove (11).

7. The unsaturated soil three-dimensional stress state dynamic testing device according to claim 1 is characterized by: The channel of the sensor data wire (10) contains sealant (112) as a filler.

8. A method for implementing the unsaturated soil three-dimensional stress state dynamic testing device according to claim 1, characterized in that: The following steps are involved: 1) Lay out the dynamic test device for the three-dimensional stress state of unsaturated soil and connect the data wire to the acquisition system; 2) With the center of the spherical body (1) as the origin, the line connecting the middle points of the top and bottom surfaces as the positive direction of the z-axis, and the line connecting the origin and the center of the surface of the arc-shaped inclination sensor (9) as the positive direction of the x-axis, a spatial rectangular coordinate system is established according to the right-hand system, and the cylindrical grooves (11) on the spherical body (1) are numbered, where A u A is a cylindrical groove (11) provided with a circular arc water-permeable plate (5), s A is a cylindrical groove (11) arranged with a circular arc clay plate (6), T The cylindrical groove (11) is provided with an arc-shaped tilt sensor (9), A1 is the cylindrical groove (11) at the top of the spherical body (1); A2, A3, A4, A5, and A6 are five adjacent cylindrical grooves (11) in the middle layer of the spherical body (1) in the clockwise direction starting from the cylindrical groove (11) of the arc-shaped water-permeable plate (5); A7, A8, A9, and A10 are five adjacent cylindrical grooves (11) in the middle layer of the spherical body (1) starting from the cylindrical groove (11) of the arc-shaped water-permeable plate (5). 10 , A 11 , A 12 , A 13 , A 14 A is arranged on the upper layer of the spherical body (1) and starts from the cylindrical groove (11) adjacent to the cylindrical groove (11) of the arc water-permeable plate (5) in the clockwise direction. 15 , A 16 , A 17 , A 18 , A 19 , A 20 , A 21 , A 22 8 adjacent cylindrical grooves (11) arranged in the lower layer of the spherical body (1) in a clockwise direction starting from the cylindrical groove (11) adjacent to the cylindrical groove (11) of the arc water-permeable plate (5); 3) starting the acquisition system and balancing the degree of the arc-shaped inclination sensor (9) according to the spatial rectangular coordinate system established in step 2), and then burying the balanced unsaturated soil three-dimensional stress state dynamic test device inside the unsaturated soil body; 4) Determine the test values ​​σ of the double-film sensor (21) in 22 directions according to the double-film sensor (21) arranged on the cylindrical groove (11) i , i=1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, wherein σ1 is the test value of the double-film sensor (21) arranged on the cylindrical groove (11) A1 of the spherical body (1), σ2, σ3, σ4, σ5, σ6 are the test values ​​of the double-film sensor (21) arranged on the cylindrical grooves (11) A2, A3, A4, A5, A6 of the spherical body (1), σ7, σ8, σ9, σ10 are the test values ​​of the double-film sensor (21) arranged on the cylindrical grooves (11) A2, A3, A4, A5, A6 of the spherical body (1), 10 , σ 11 , σ 12 , σ 13 , σ 14 A7, A8, A9, A 10 , A 11 , A 12 , A 13 , A 14 Test value of the double-film sensor (21) on the cylindrical groove (11), σ 15 , σ 16 , σ 17 , σ 18 , σ 19 , σ 20 , σ 21 , σ 22 Arranged in the spherical body (1) A 15 , A 16 , A 17 , A 18 , A 19 , A 20 , A 21 , A 22 Test value of the double-film sensor (21) on the cylindrical groove (11), σ u Arranged in the spherical body (1) A u Test value of strain gauge sensor on cylindrical groove (11), σ s Arranged in the spherical body (1) A s The test values ​​of the strain gauge sensor on the cylindrical groove (11), θ, η, ζ are respectively arranged on the spherical body (1) A T Angles around the z, y and x axes collected by the arc-shaped inclination sensor (9) on the cylindrical groove (11); 5) Using formula (1), calculate σ on the dynamic test device for three-dimensional stress state of unsaturated soil i The effective stress value σ in the direction i ', where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, formula (1) is: in i =s i -(s s +s u )+S e s s (1) In the formula, σ i ' is the A value of the dynamic test device for the three-dimensional stress state of unsaturated soil i The effective stress values ​​on the cylindrical groove (11), i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, σ i Arranged in the spherical body (1) A i Test value of the double-film sensor (21) on the cylindrical groove (11), σ u Arranged in the spherical body (1) A u Test value of strain gauge sensor on cylindrical groove (11), σ s Arranged in the spherical body (1) A s Test value of strain gauge sensor on cylindrical groove (11), S e is the effective degree of saturation of unsaturated soil; 6) Based on the spatial rectangular coordinate system established in step 2), σ i Direction is the unit vector through the origin Expressed as follows, where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22; 7) Use formula (2) to convert the dynamic test direction vector of the dynamic test device for three-dimensional stress state of unsaturated soil into Expressed as follows, formula (2) is: In the formula, is the dynamic test direction vector of the dynamic test device for three-dimensional stress state of unsaturated soil, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, θ, η, ζ are arranged on the spherical body (1) A respectively T The angles around the z, y and x axes collected by the arc-shaped inclination sensor (9) on the cylindrical groove (11) are is i A unit vector whose direction passes through the origin; 8) The direction cosine D of the dynamic test direction of the dynamic test device for three-dimensional stress state of unsaturated soil i {l i ',m i ',n i '} Calculated using formulas (3), (4), and (5), the formula is: In the formula, l i '、m i '、n i ' is the direction cosine of the dynamic test direction of the dynamic test device for three-dimensional stress state of unsaturated soil, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, is the dynamic test direction vector of the dynamic test device for the three-dimensional stress state of unsaturated soil, is the vector norm of the dynamic test direction of the dynamic test device for the three-dimensional stress state of unsaturated soil, are the unit vectors on the x, y, and z axes respectively, are the magnitudes of the unit vectors on the x, y, and z axes respectively; 9) Select 6 different direction cosines D i {l i ',m i ',n i '} Construct the transformation matrix M shown in formula (6), where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, and denote the selected direction cosines as D i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '}, formula (6) is: Where M is the transformation matrix, D i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '} are 6 different direction cosines selected, i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22; 10) Calculate the inverse matrix M of the matrix M in formula (6) -1 , and the dynamic value {σ} of the three-dimensional stress state of unsaturated soil is calculated according to formula (7), which is: {σ}=M -1 ·{σ′ ij } (7) Where {σ} is the dynamic value of the three-dimensional stress state of unsaturated soil, M -1 is the inverse matrix of matrix M, {σ′ ij ] is the direction cosine D in step 9) determined according to formula (1) i1 {l i1 ',m i1 ',n i1 '}、D i2 {l i2 ',m i2 ',n i2 '}、D i3 {l i3 ',m i3 ',n i3 '}、D i4 {l i4 ',m i4 ',n i4 '}、D i5 {l i5 ',m i5 ',n i5 '}、D i6 {l i6 ',m i6 ',n i6 '} The effective stress value σ in the direction corresponding to i ', i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, j is 6 different direction cosines D i {l i ',m i ',n i '} are numbered in sequence, j=1, 2, 3, 4, 5, 6.

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